Oscar Castellanos is a Spanish voice actor known for his work in dubbing anime and live-action productions into Spanish. He began his career in the mid-2000s and has balanced his work in dubbing with a concurrent career as a television presenter in Spain.

Castellanos has voiced a variety of characters in anime, with one of his most notable roles being Colonel Muska in the Spanish dub of the Studio Ghibli film Castle in the Sky. He has also contributed his voice to other Ghibli films, such as Koichi in Ponyo on the Cliff by the Sea and the King in Tales from Earthsea. His work in the anime industry extends to long-running series, including several roles in the Pokémon franchise. He has voiced Freddy O'Martin in Pokémon: Black and White and its sequel Rival Destinies, as well as Professor Sycamore in Pokémon XY and Pokémon XY & Z, and the character Jason in Pokémon the Movie: The Power of Us. Other anime credits include roles in D.Gray-man, Zatch Bell, Sword Gai: The Animation, and Super GALS!. Beyond animation, his dubbing work also encompasses live-action films such as Blade of the Immortal and Air Doll.